Perpendicular magnetic recording (PMR) writer main poles are conventionally formed in trenches of non-magnetic or insulating materials. The PMR writer main pole is a trapezoidal formation of magnetic material deposited in a trapezoidal trench etched in a surrounding material. Before deposition of the magnetic material, the trench is plated in a seed layer of non-magnetic material. The plating seed provides a void-free fill of the trench with the magnetic material while retaining desirable properties such as high saturation magnetization, low easy/hard axis coercivity, low anisotropy, high frequency response, and low remnant magnetization.
In some cases, the writer main pole may be encapsulated with a soft magnetic shield layer. In this application, a plating seed layer in the trench is also used. In both applications, Ru is conventionally used as the plating seed layer. Conventionally, atomic layer deposition (ALD) and conformal chemical vapor deposition (CVD) are the only commercially viable methods to provide conformal Ru deposition.
In one conventional process, an RuO4-containing mixture is used as the Ru precursor and H2 as the co-reactant of RuO4 to deposit a highly conductive and continuous Ru film. However, the step coverage of the CVD Ru process alone is poor because field, trench sidewall, and trench bottom are usually different materials. Conventionally, a seed layer is deposited between the trench and the CVD Ru layer using a physical vapor deposition (PVD) process. Even with this combination, the bottom gap is thinner than the side gap because of re-deposition and sputtering during pre-cleaning etching. For example, the conventional process typically results in less a bottom gap to side gap (BG/SG) ratio of less than 88%. It is expected that the writer field (Hv) will decrease significantly as the bottom gap (also known as the leading gap (LG)) decreases from 60 nm to 40 nm. Accordingly, with increasing miniaturization the decreased thickness of the bottom gap will increasingly degrade writeability.